Gauges
GaugesAll gauges receive battery current through the EMIC circuitry when the ignition switch is in the ON or Start positions. With the ignition switch in the OFF position battery current is not supplied to any gauges, and the EMIC circuitry is programmed to move all of the gauge needles back to the low end of their respective scales. Therefore, the gauges do not accurately indicate any vehicle condition unless the ignition switch is in the ON or Start positions. All of the EMIC gauges, except the odometer, are air core magnetic units. Two fixed electromagnetic coils are located within each gauge. These coils are wrapped at right angles to each other around a movable permanent magnet. The movable magnet is suspended within the coils on one end of a pivot shaft, while the gauge needle is attached to the other end of the shaft. One of the coils has a fixed current flowing through it to maintain a constant magnetic field strength. Current flow through the second coil changes, which causes changes in its magnetic field strength. The current flowing through the second coil is changed by the EMIC circuitry in response to messages received over the PCI data bus. The gauge needle moves as the movable permanent magnet aligns itself to the changing magnetic fields created around it by the electromagnets.
The gauges are diagnosed using the EMIC self-diagnostic actuator test. Proper testing of the PCI data bus and the data bus message inputs to the EMIC that control each gauge require the use of a DRB III scan tool. Refer to the appropriate diagnostic information. Specific operation details for each gauge may be found elsewhere in this service information.
ENGINE TEMPERATURE GAUGE
An engine coolant temperature gauge is standard equipment on all instrument clusters. The engine coolant temperature gauge is located in the lower right quadrant of the instrument cluster, below the oil pressure gauge. The engine coolant temperature gauge consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 90 degree scale on the cluster overlay that reads left-to-right from 40 °C (or 100 °F) to 125 °C (or 260 °F). An International Control and Display Symbol icon for "Engine Coolant Temperature" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. The engine coolant temperature gauge graphics are white and blue against a black field except for a single red graduation at the high end of the gauge scale, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned ON, the white graphics appear white, the blue graphics appear blue, and the red graphics appear red. The orange gauge needle is internally illuminated. Gauge illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The engine coolant temperature gauge is serviced as a unit with the instrument cluster.
The engine coolant temperature gauge gives an indication to the vehicle operator of the engine coolant temperature. This gauge is controlled by the instrument cluster electronic circuit board based upon the cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The engine coolant temperature gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position.
The instrument cluster circuitry controls the gauge needle position and provides the following features:
* Engine Temperature Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is between about 40 °C (100 °F) and 124 °C (255 °F), the gauge needle is moved to the appropriate linear position on the gauge scale to represent the actual engine temperature. The gauge needle will continue to be positioned at the actual temperature position on the gauge scale until the cluster receives a message from the PCM that indicates the engine temperature is low, high, or critical, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Engine Temperature Low Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is at or below about 40 °C (100 °F), the gauge needle is held at the 40 °C (100 °F) graduation at the far left end of the gauge scale. The gauge needle remains at the far left end of the scale until the cluster receives a message from the PCM indicating that the engine temperature is above about 40 °C (100 °F), or until the ignition switch is turned to the OFF position, whichever occurs first.
* Engine Temperature High Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is about 127 °C or higher (about 261 °F or higher), the gauge needle is moved to the center of the red zone on the gauge scale, the check gauges indicator is illuminated, and a single chime tone is sounded. The chime tone feature will occur only once per ignition cycle. The gauge needle remains in the center of the red zone and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating that the engine temperature is about 124 °C or lower (about 255 °F or lower), or until the ignition switch is turned to the OFF position, whichever occurs first.
* Engine Temperature Critical Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is about 129 °C or higher (about 264 °F or higher), the gauge needle is moved to the far right end of the red zone on the gauge scale. The gauge needle remains at the far right end of the red zone until the cluster receives a message from the PCM indicating that the engine temperature is about 127 °C or lower (about 261 °F or lower), or until the ignition switch is turned to the OFF position, whichever occurs first.
* Message Failure - If the cluster fails to receive an engine temperature message for more than about twelve seconds, it will move the gauge needle to the minimum graduation of the gauge scale until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Actuator Test - Each time the cluster is put through the actuator test, the gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM then sends the proper engine coolant temperature messages to the instrument cluster. If the instrument cluster turns on the check gauges indicator due to a high or critical engine temperature gauge reading, it may indicate that the engine or the engine cooling system requires service. For proper diagnosis of the engine coolant temperature sensor, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the engine coolant temperature gauge, a DRBIII scan tool is required Refer to the appropriate diagnostic information.
FUEL GAUGE
A fuel gauge is standard equipment on all instrument clusters. The fuel gauge is located in the lower left quadrant of the instrument cluster, below the voltage gauge. The fuel gauge consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 90 degree scale on the cluster overlay that reads left-to-right from E (or Empty) to F (or Full). An International Control and Display Symbol icon for "Fuel" is located on the cluster overlay in the center of the gauge directly above the hub of the gauge needle. An arrowhead icon pointed toward the left side of the vehicle is imprinted on the cluster overlay next to the "Fuel" icon in the fuel gauge to provide the driver with a reminder as to the location of the fuel filler access. The fuel gauge graphics are white and blue against a black field except for a single red graduation at the low end of the gauge scale, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned ON, the white graphics appear white, the blue graphics appear blue, and the red graphics appear red. The orange gauge needle is internally illuminated. Cluster illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The fuel gauge is serviced as a unit with the instrument cluster.
The fuel gauge gives an indication to the vehicle operator of the level of fuel in the fuel tank. This gauge is controlled by the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The fuel gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position.
The instrument cluster circuitry controls the gauge needle position and provides the following features:
* Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full, the cluster programming applies an algorithm to calculate the proper gauge needle position, then moves the gauge needle to the proper position on the gauge scale. The algorithm is used to dampen gauge needle movement against the negative effect that fuel sloshing within the fuel tank can have on accurate inputs from the fuel tank sending unit to the PCM. The gauge needle will continue to be positioned at the proper position on the gauge scale until the cluster receives a message from the PCM that indicates the percent tank full is less than empty, more than full, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Less Than 12.5 Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating that the percent tank full is less than 12.5 (one-eighth), the gauge needle is moved to the proper position on the gauge scale, the low fuel indicator is illuminated, and a single chime tone is sounded. The low fuel indicator remains illuminated until the cluster receives messages from the PCM for a continuous twenty seconds indicating that the percent tank full has increased by more than 0.625 gallons or until the ignition switch is turned to the OFF position, whichever occurs first. This strategy is intended to reduce the effect that fuel sloshing within the fuel tank can have on reliable indications. The chime tone feature will occur only once per ignition cycle.
* Less Than Empty Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating that the percent tank full is less than empty, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately This message would indicate that the fuel tank sender input to the PCM is a short circuit.
* More Than Full Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is more than full, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately. This message would indicate that the fuel tank sender input to the PCM is an open circuit.
* Message Failure - If the cluster fails to receive a percent tank full message, it will hold the gauge needle at the last indication for about twelve seconds, until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first. After about twelve seconds, the gauge needle is moved to the far left (low) end of the gauge scale and the low fuel indicator is illuminated immediately.
* Actuator Test - Each time the cluster is put through the actuator test, the gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the fuel tank sending unit, then sends the proper messages to the instrument cluster. For proper diagnosis of the fuel tank sending unit, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the fuel gauge, a DRBIII scan tool is required Refer to the appropriate diagnostic information.
OIL PRESSURE GAUGE
An oil pressure gauge is standard equipment on all instrument clusters. The oil pressure gauge is located in the upper right quadrant of the instrument cluster, above the engine coolant temperature gauge. The oil pressure gauge consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 90 degree scale on the cluster overlay that reads left-to-right from 0 kg/cm (or 0 psi) to 5.4 kg/cm (or 80 psi). An International Control and Display Symbol icon for "Engine Oil" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. The oil pressure gauge graphics are white and blue against a black field, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned ON, the white graphics appear white, and the blue graphics appear blue. The orange gauge needle is internally illuminated. Gauge illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The oil pressure gauge is serviced as a unit with the instrument cluster.
The oil pressure gauge gives an indication to the vehicle operator of the engine oil pressure. This gauge is controlled by the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The oil pressure gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position.
The instrument cluster electronic circuitry controls the gauge needle position and provides the following features:
* Engine Oil Pressure Message - Each time the cluster receives a message from the PCM indicating the engine oil pressure is between about 0.3 kg/cm (4 psi) and about 6.7 kg/cm (95 psi), the cluster moves the gauge needle to the appropriate linear position on the gauge scale to represent the actual engine oil pressure. The gauge needle will continue to be positioned at the actual engine oil pressure position on the gauge scale until the cluster receives a message from the PCM that indicates the engine oil pressure is low, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Engine Oil Pressure Low Message - Each time the cluster receives a message from the PCM indicating the engine oil pressure is below about 0.3 kg/cm (4 psi), the gauge needle is moved to the minimum increment on the far left (low) end of the gauge scale, the check gauges indicator is illuminated, and a single chime tone is generated. The gauge needle remains at the low end of the scale and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating that the engine oil pressure is about 0.6 kg/cm (8 psi) or higher, or until the ignition switch is turned to the OFF position, whichever occurs first. The cluster will only turn the check gauges indicator on in response to an engine oil pressure low message if the engine speed is 300 rpm or greater for more than about five seconds.
* Message Failure - If the cluster fails to receive an engine oil pressure message for more than about twelve seconds, it will move the gauge needle to the minimum graduation of the gauge scale until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Actuator Test - Each time the cluster is put through the actuator test, the gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the engine oil pressure sensor to determine the engine oil pressure. The PCM then sends the proper engine oil pressure messages to the instrument cluster. If the instrument cluster turns on the check gauges indicator due to a low oil pressure gauge reading, it may indicate that the engine or the engine oiling system requires service. For proper diagnosis of the engine oil pressure sensor, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the oil pressure gauge, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.
VOLTAGE GAUGE
A voltage gauge is standard equipment on all instrument clusters. The voltage gauge is located in the upper left quadrant of the instrument cluster, above the fuel gauge. The voltage gauge consists of a movable gauge needle or pointer controlled by the instrument cluster electronic circuitry and a fixed 90 degree scale on the cluster overlay that reads left-to- right from 9 volts to 19 volts. An International Control and Display Symbol icon for "Battery Charging Condition" is located on the cluster overlay, in the center of the gauge directly above the hub of the gauge needle. The voltage gauge graphics are white and blue against a black field except for a single red graduation at each end of the gauge scale, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned ON, the white graphics appear white, the blue graphics appear blue, and the red graphics appear red. The orange gauge needle is internally illuminated. Gauge illumination is provided by replaceable incandescent bulb and bulb holder units located on the instrument cluster electronic circuit board. The voltage gauge is serviced as a unit with the instrument cluster.
The voltage gauge gives an indication to the vehicle operator of the electrical system voltage. This gauge is controlled by the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The voltage gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position.
The instrument cluster circuitry controls the gauge needle position and provides the following features:
* System Voltage Message - Each time the cluster receives a message from the PCM indicating the system voltage, the gauge needle is moved to the actual system voltage position on the gauge scale. The gauge needle will continue to be positioned at the actual system voltage position on the gauge scale until the cluster receives a message from the PCM that indicates the system voltage is low (charge fail), high, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Charge Fail Message - Each time the cluster receives a message from the PCM indicating a charge fail condition (system voltage is nine volts or lower), the gauge needle is moved to the 9 volt graduation on the gauge scale and the check gauges indicator is illuminated. The gauge needle remains on the 9 volt graduation and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating there is no charge fail condition (system voltage is twelve volts or higher, but lower than sixteen volts), or until the ignition switch is turned to the OFF position, whichever occurs first.
* Voltage High Message - Each time the cluster receives a message from the PCM indicating a voltage high condition (system voltage is nineteen volts or higher), the gauge needle is moved to the 19 volt graduation on the gauge scale and the check gauges indicator is illuminated. The gauge needle remains ON the 19 volt graduation and the check gauges indicator remains illuminated until the cluster receives a message from the PCM indicating there is no voltage high condition (system voltage is sixteen volts or lower, but higher than nine volts), or until the ignition switch is turned to the OFF position, whichever occurs first.
* Message Failure - If the cluster fails to receive a system voltage message for more than about twelve seconds, it will move the gauge needle to the minimum graduation of the gauge scale until a new message is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
* Actuator Test - Each time the cluster is put through the actuator test, the gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the system voltage to control the generator output. The PCM then sends the proper system voltage messages to the instrument cluster. If the instrument cluster turns ON the check gauges indicator due to a charge fail or voltage high condition, it may indicate that the charging system requires service. For proper diagnosis of the charging system, the PCI data bus, or the message inputs to the instrument cluster that control the voltage gauge, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.